1. Field of the Invention
The present invention relates generally to conveyor systems and belts therefor and, more particularly, to conveyor belts capable of traversing relatively small radius horizontal curves.
2. Background of the Prior Art
At least three types of conveyor belts are in general use today for carrying diverse products along both straight and horizontally curved paths. The first type generally referred to as a grid belt is illustrated in U.S. Pat. No. 3,225,898. Such a belt comprises a plurality of spaced transverse rods slidably interconnected by two rows of connecting links disposed along the inner and outer edges of the rods. The connecting links are disposed in a nested relationship relative to one another with slots in the links slidably receiving the rods. Either edge of the belt can suitably collapse when it is necessary for the belt to travel around a horizontal curve.
The second type of belt, generally referred to as a flat wire belt, is illustrated in U.S. Pat. No. Re. 27,690. In the flat wire belt, the transverse rods are slidably interconnected by transversely disposed flat wire tractive links having a width spanning substantially the entire length of the rods. The tractive links comprise a plurality of longitudinally disposed tractive members secured together by transversely disposed connecting members to form a plurality of U-shaped segments. Longitudinal slots are provided in the tractive members for slidably receiving the rods. As in the case of the grid type belt, the tractive links are arranged in a nested relationship relative to one another to enable the belt to collapse along either edge to traverse horizontal curves. In addition, reinforcing bar links are often placed along the outer edges of the flat wire belt for bearing the tractive load on the belt as it traverses the curve to prevent fatigue failure of the flat wire links.
The third type of belt noted above, which may be referred to as the center pull belt, is illustrated generally in U.S. Pat. No. 3,467,239 and the British Pat. No. 738,806 to Ravestein. In this type, the transversely disposed rods are connected at their central portions by tractive links or a chain, which carries the entire tractive load as the belt travels both in a straight path and around horizontal curves. When the belt is traversing such a curve, the inner ends of the rods will move closer together and the outer ends of the rods will separate. Although the rods in these belts are often unconnected to each other, except for their attachment to the center pull device, nontractive support links have been placed between the rods to help carry the products placed thereon as shown in the Ravestein patent.
Grid and flat wire belts have enjoyed substantial commercial success because of their ability to traverse horizontal curves while still providing an integrated carrying surface capable of supporting a great variety of products. Another desirable feature of such belts is that they can pass freely in vertical curves around relatively small end pulleys. However, these belts have the disadvantageous limitation of a relatively large horizontal turning radius which limits their usefulness in some conveyor installations. For example, this disadvantage limits the width of the belt and thus its carrying capacity in certain low tension conveying systems of the type generally shown in U.S. Pat. No. 3,348,659.
The center pull belts have not met with substantial success and have definite disadvantages. The entire tractive load on such a belt is always borne by the center pull device. Thus, a relatively large and strong center pull device is required. Moreover, the lack of any tractive connection or other adequate support along the outer rod ends renders the edges of the belt very unstable. In addition, the center chain pull belts, as exemplified by Ravestein, require relatively large end pulleys.